Wednesday, 19 February 2014

Chill Kills

After all the hard work the other yeast girls and I have put into culturing our microscopic friends, it is sadly now time to start killing them! 

Some of the earlier ferments that we prepared have dropped to the targeted sugar level (in the wine industry, this is termed Baume) and the environment in the tanks is already becoming less comfortable for the yeast for two reasons:
1. They are running out of food
2. They cannot tolerate high ethanol levels 
The latter of these two points is quite ironic, seeing as the alcohol is their own by-product!

To make the situation even more difficult for the yeast, we chill the tanks down to 5 degrees Celcius (yeast don't like the cold) and then add sulphur dioxide (toxic to yeast at certain levels) and some fining agents to ensure the dead yeast cells settle to the bottom of the tank for separation.
sulphur gun being filled with liquid sulphur dioxide
I feel like a cold-hearted killer... but I think the end product is worth it!